The two principal objectives of the research are (a) to determine the interrelationships between prostaglandin (PG) biosynthesis, antidiuretic hormone (ADH) action and 3',5'-cAMP levels in collecting tubule epithelial cells from rabbit renal medulla and (b) to determine the subcellular location of the cyclooxygenase catalyzing the formation of prostaglandin endoperoxides in renal collecting tubule epithelial cells and renal arterial endothelial cells. Our long range goal is to delineate the function of PGs formed in the renal collecting tubules.